2-1 splitter-like jack to be used with CAT5 cables?

Discussion in 'Linux Networking' started by Albretch Mueller, Sep 16, 2005.

  1. Hi *,

    is there such a thing as a 2-1 splitter-like jack like the ones they use for
    telephones or broadband/DSL modems with more than one outgoing connector?

    Or should people use a front telephone splitter and 2 DSL modems?

    Albretch Mueller, Sep 16, 2005
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  2. Albretch Mueller

    lbrtchx Guest

    as I understand things DSL modems do NOT do MAC address nothing. They are
    just modems; the actual MAC address is provided by the switch, hub or NIC
    of the computer used and you can always convine with your ISP to register
    more than one MAC address in their ARP tables cache assigned to you. Right?

    I think I must still be missing something here ;-)

    Say you have a ha (high availability) setup with two routers a
    'primary/production' one, acting as director to the server cluster, and a
    'backup' one, how does the backup one take over when the primary fails
    without such a device?

    Both MUST be right after the Internet connection device/DSL modem/...,

    The software part of it (I think) I do understand, but there is this
    missing piece in my understanding of the whole picture

    There must be some kind of sharing on the Link Layer. How is it done?

    lbrtchx, Sep 16, 2005
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  3. Albretch Mueller

    Joe Pfeiffer Guest

    Ummm, what is it you really want to do?

    Trying to answer your questions in reverse order, the second option
    you suggest simply won't work. The two modems will just be stepping
    on each other in trying to talk on the line.

    I've got a hunch what you're really asking for with the first option
    is whether there is a way to put two computers on the output from a
    single DSL modem. If I'm guessing right, the answer is "yes, but it
    doesn't look much like a phone Y-jack and internally doesn't work
    anything like the same way." What you're looking for here is a
    "router" with multiple ethernet jacks on the downstream side (assuming
    I'm guessing right on your actual goal).
    Joe Pfeiffer, Sep 16, 2005
  4. Based on similar assumptions, my setup could be an example. I have an
    ADSL modem and two computers. The ADSL modem speaks PPPoE,
    "Point-to-Point Protocol (o)ver Ethernet". In the middle I have an
    "ethernet" hub.

    (I say "ethernet" in quotes, because the modern equipment running
    IEEE 802-dot-something is a bit different from the original ethernet,
    but we all keep saying "ethernet". The data contents of the packets
    is identical, though.)

    Because of the nature of the PPPoE protocol, only one of my PC's can
    talk directly to the ADSL modem. But I don't have to flip switches or
    disconnect or connect cables to change. I let the first PC establish
    the conversation with the ADSL modem, but if that PC goes down or
    anything, I just enable the second PC to do the same with a keystroke.

    Whichever PC has the PPPoE conversation tells the other and serves as
    gateway to the internet. The two PCs have identical firewall/nat
    masquerading set up, but the non-gateway will never see its firewall
    rules triggered.

    When the two PCs talk to eachother, the communication goes through
    the same hub. Yet, the communication between the PCs is IP datagrams
    while the communication between the gateway and the ADSL modem is not.
    But they are all "ethernet" datagrams. The hub only sees the data as
    ethernet packets with some (varying) kind of payload. The hub does
    not care what the payload is.

    Even if the packets go throught the same wires and the same hub, all
    the IP datagrams are "inside" the firewall. The PPPoE datagrams
    carry the "outside" traffic like in a tunnel.

    Compared to Joe's proposed router, my hub is more like a dead wire,
    but the PC that is serving as the gateway is the router.

    Enrique Perez-Terron, Sep 17, 2005
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